Arduino is simple and very powerfull open source/hardware platform where only your imagination can stop you.A few days ago I read an instructable that inspire me to do my own.The instructable is about how you can send strings of data from one arduino to another.Everything is ok but I wanted to make it with Attiny85 .but unfortunately libraries are not supported with this microcontroller.So, I need to find a way how to generate 38khz and send modulated data and how to translate those data.I'm not enough pro :) to know how attiny85 to generate 38khz itself so I used old good one 555 timer.Everything is good but now I must to send data somehow.There are 3 possibilities:

1-By controling reset pin of the 555 timer

2-switching on/off power supply of 555 timer

3-switching on/off LEDs(timer is always on)

I used 3th variant.

Let's start!

Step 1: Parts list

Microcontrollers and timers:

1x555 timer

1xATtiny85(you can use any microntroller from Attiny family)

Resistors and trimers/pots:

1x10k

3x4.7k

1x22k

1x10k trimer/pot

Capacitors:

1x1nF

1x100nF

1x10uF/16v

Transistors:

Any pnp/npn transistors.In this project I used 1xBC547(npn) and 1xBC327(pnp)

Sensors:

LM35DZ couse it's easy to use

Regulators:

78l05(7805)

LEDs and transmitters:

Any IR leds.

You can use any ir receiver.Why??Because you can tune to the right frequence 555 timer with 10k trim/pot.

NOTE:

*To be exactly 38khz you must to tune trimer/pot around 7.979k or just mesure frequency with multimeter

*Supply voltage can be everything between 6.8v-30v*Attiny85 is running at 16mhz internal oscillator

Step 2: Shematic and pinouts

Step 3: Transmitter code

After you finished with circuit you must to upload some code..right? :D

In my project I used morse alphabet to send data.

There are two files, first one is little modified Morse library and the second file is main program.I uploaded the code trought Arduino with tiny cores.You can find it here:http://code.google.com/p/arduino-tiny/downloads/detail?name=arduino-tiny-0100-0018.zip

Morse.rar2 KB

MorseIR.rar760 bytes

Step 4: Receiver code

It can be done a lot of optimizations.Because now you can only send numbers(in my case temperature).

ReceiverIR.rar758 bytes

Step 5: Update

Couple pictures how I integrated this circuit.

ReceiverIR.ino1 KB

Step 6: Final product

Basic characteristics:-consumption:7-10mA-range:3-6m

Next goals:

Single chip solution, less power consuptionPlease comment and share your ideas for improving this device.Thanks for reading!